1. Field of the Invention
The invention relates to food product cans provided with can end members which may be opened easily by tearing with a ring pull tab, a full opening removable panel portion to which the tab is riveted, along an endless score line formed in the can end member, particularly a can end of a can used for food products that are heat-processed in the closed can; and more particularly, to providing stiffness to relatively thin sheet metal can end material in the removable panel portion, whether or not the removable panel portion is provided with a protective fold at the peripheral edge of the removed panel, so as to obtain maximum rupturing force in initiating, without tab rivet connection damage, rupture of the score line defining the removable panel portion when initially lifting the ring pull tab riveted to the panel portion, and also particularly to such a construction in which the apparent force required to remove the severed panel is less because of the stiffness of the embossed panel.
2. Description of the Prior Art
Many prior patents show various kinds and types of embossed formations in the can end of a can adapted to be opened by tearing the can end along one or more score lines to remove the can end, tear strip fashion, as in U.S. Pat. Nos. 2,112,231, 3,195,768, 3,221,923, and 3,416,699; or to remove the can end of a full opening can along a circumscribing score line as in U.S. Pat. Nos. 3,478,918, 3,712,503, 3,715,050, 3,735,892, and 3,768,692.
These prior can end structures contain embossed formations in the tear strip type of can end for directing the tearing properly along the score lines defining the tear strip. The prior structures in the case of full opening can ends in which a panel is removed by tearing along a continuous circumscribing score line have panel embossed formations to direct, control and implement the curling of the removed panel portion as it is being peeled from the can.
No can end structure of which we are aware has been provided with means such as an embossed formation in the can end for maintaining the can end stiff and in substantially a flat plane during the moment of initial application of rupturing force by the nose of a pull tab riveted to the removable panel portion to initiate rupture along the score line defining the removable portion, so that the rupturing force is applied to the can end adjacent the score line in as near to a vertical direction as possible so as to shear the metal on the score line, rather than to tear it.
Further, no prior structure of a full opening can end of which we are aware is provided with an embossed reinforcing formation in its removable panel, which provides full opening of the can, whether or not the removable panel has a protective formation at the edge thereof, in which the removable panel is maintained substantially stiff and flat or planar in extent, as the panel is pulled upward and removed by severing along the major portion of its periphery after an initial segment thereof has been bent inward of the can upon initiation of rupture by downward force applied by the nose of the pull tab riveted to the removable panel portion.
The use of easy opening cans in the heat-processed canned food industry has resulted in many problems concerning the construction and opening of such cans because of the tendency of the can end to dome or bulge outward or inward as a result of pressure or vacuum forces occurring in connection with heat-processing of the food in the cans. Such doming or bulging may affect the manner or direction in which force is applied by a ring pull tab to the can end material initially to rupture and later to pull the removable panel portion from the can along the score line defining the removable panel portion.
Some of these difficulties may be minimized by providing heavier gauge metal for the can ends and ring pull tabs. Such solution of the problems, however, is unsatisfactory, not only because of the cost of and use of additional metal, but also because it affects the ability to manufacture and handle the can ends and pull tabs in the production and manufacture thereof in existing tool and die means designed for lighter gauge metals.
Accordingly, there exists a need for overcoming the deficiencies in prior removable panel can end and pull tab structures without increasing metal thickness, and at the same time providing for applying maximum rupturing force and apparent minimum lifting force by the pull tab to the removable panel portion when a full opening, easy opening can is opened.